A method for preparing a supported organometallic complex is disclosed. An organometallic complex is combined with a support material that has been treated with an organozinc compound. The organometallic complex comprises a Group 3 to 10 transition metal and an indenoindolyl ligand that is bonded to the transition metal. Also disclosed is a process for polymerizing an olefin using the supported complex. Organozinc treatment of the support unexpectedly boosts catalyst activity and polyolefin molecular weight.